Method and apparatus for neurophysiologic performance

ABSTRACT

The invention features methods and apparatus for enhancing neurophysiologic performance, such as sensorimotor control and neuroplasticity. A preferred method involves inputting bias signals to sensory cells of a subject, thereby improving sensory cell function, while the subject is performing a predefined physical activity. A system used to practice the method of the invention includes a wearable device to which is secured at least one repositionable signal input device and a signal generator that is communicatively coupled to the signal input devices.

[0001] RELATED U.S. APPLICATION DATA

[0002] This application is a non-provisional application of U.S.provisional patent application No. 60/377,202.

BACKGROUND OF THE INVENTION

[0003] 1. Field of the Invention

[0004] This invention relates to methods and apparatus for enhancingneurophysiologic performance, such as sensorimotor control andneuroplasticity, by combining improved function of sensory cells withpre-defined physical activity and use of certain devices.

[0005] 2. Description of Related Art

[0006] The nervous system of mammals is a complex set of interrelatedand interacting sub-systems. The sub-systems are categorized and namedboth by their anatomic positions and by their function. At the highestlevel, the nervous system is divided into central and peripheral nervoussystems. The central nervous system (CNS) is comprised of the brain andspinal cord; the peripheral nervous system (PNS) subsumes all theremaining neural structures found outside the CNS. The PNS is furtherdivided functionally into the somatic (voluntary) and autonomic(involuntary) nervous systems. The PNS can also be describedstructurally as being comprised of afferent (sensory) nerves, whichcarry information toward the CNS, and efferent (motor) nerves, whichcarry commands away from the CNS.

[0007] Interconnections between afferent and efferent nerves are foundin the spinal cord and brain. Taken together, certain groupings ofafferent and efferent nerves constitute sensorimotor “loops” that arerequired to achieve coordinated movements in the face of perturbationsfrom the environment and changes in volitional intent. In the periphery(trunk, upper extremities, and lower extremities), afferent nerves carrysensory information arising from special neurons that are sensitive topain, temperature, and mechanical stimuli such as touch and vibration atthe skin surface, and position, force, and stretch of deeper structuressuch as muscles, tendons, ligaments, and joint capsule. The term“proprioception” generally applies to sensory information directlyrelevant to limb position sense and muscle contraction. Combined withtactile (touch) sensation, mechanical sensory information iscollectively known as “somatosensation.”

[0008] Specialized “mechanoreceptor” neurons transduce mechanicalstimuli from the body's interaction with the environment into electricalsignals that can be transmitted and interpreted by the nervous system.Pacinian corpuscles in the skin fire in response to touch pressure.Muscle spindles, found interspersed in skeletal muscle tissue, report onthe state of stretch of the surrounding muscle. Golgi tendon organssense the level of force in the tendon. Free nerve endings in structuressurrounding joints (ligaments, meniscus, etc.) provide additionalinformation about joint position. Some of these mechanoreceptor systemsare thought to interact directly via excitatory and inhibitory synapsesand descending pathways to modulate the performance or interpretation ofsignals from other mechanoreceptor systems.

[0009] Sensory cells of all types are typically threshold-based units.That is, if the stimulus to a sensory cell is of insufficient magnitude,the cell will not activate and begin signaling. Such a stimulus iscalled “subthreshold.” A stimulus that is above the threshold is called“suprathreshold.”

[0010] Connections within the nervous system-brain, spinal cord, andperipheral nerves—are highly changeable in the face of demands placed onthe body: new forms of activity, pathologies, and injuries. In healthyindividuals, these neurological changes allow for the acquisition of newphysical skills, a process termed “motor learning.” Following certaintypes of soft tissue injury (e.g. rupture of the anterior cruciateligament of the knee, a structure known to be rich in mechanoreceptors),and subsequent medical efforts such as surgery used to repair thedamage, the nervous system can undergo compensatory changes toaccommodate for loss of the natural sensory neurons. Similar PNS and CNSnervous system changes account for some individual's ability to regainlost motor function following spinal or brain injuries. Taken together,these structural changes in the nervous systems are termed“neuroplasticity” or “neuroplastic changes.”

[0011] Recent research has established that afferent (sensory) activityfrom the periphery is one of the key drivers of neuroplastic changes inthe nervous system, both in the PNS and CNS.

[0012] The present invention focuses on mechanical sensory neurons inthe periphery and the role they play, specifically, in sensorimotorcontrol and in inducing neuroplastic changes in the nervous system. Inthis invention, we combine prior art methods of improving theperformance of individual sensory cells with novel methods and apparatusto achieve improvements in sensorimotor control and neuroplasticity.Importantly, the nature of the improved sensory cell performance is thatthe natural firing rate in response to environmental stimuli isincreased in an information-rich fashion. That is, the increased sensorycell firing is concordant with limb function and hence is not gratuitousor uncoordinated in nature.

[0013] Electrical stimulation of tissue has been used for varioustherapeutic purposes including stimulating muscle activity, relievingpain, and producing sensation. The sequence of effects produced byelectrical stimulation, as its intensity is increased, generally followsa pattern of a perception of an electrical sensation (such as tingling),an increase in sensation, fasciculation muscle contraction, pain, andthen injury in the form of electrical burns or cardiac arrhythmias.

[0014] In the past, pulsed electrical waveforms having an adjustablepulse duration, intensity and pulse width have been applied to aparticular area of the human body for therapeutic purposes to suppresspain. Electrical waveform therapy, such as that disclosed in U.S. Pat.No. 5,487,759 to Bastyr, et al. has been used for symptomatic relief andmanagement of chronic, post surgical and posttraumatic acute pain andfor inducing muscle contraction for the retardation of atrophy.

[0015] Stimulation below perception levels (i.e. subthresholdstimulation) used to enhance the function of sensory cells is describedin U.S. Pat. Nos. 5,782,873 and 6,032,074 to Collins, the entirecontents of which are incorporated by reference. Collins discloses amethod and apparatus for improving the function of sensory cells byeffectively lowering their threshold of firing. Briefly, a subthresholdstimulation, or “bias signal,” is input to the sensory neuron thatpredisposes the neuron to firing, without actually causing it to fire.In one preferred embodiment, the bias signal is a broadband signalcontaining many frequencies, often termed “noise.” Since sensory cellsare typically threshold-based units, lowering the sensory cell thresholddecreases the level of outside stimulus needed to cause the sensory cellto respond (i.e. fire). Thus, the sensory cell, in the presence of thebias signal, is expected to respond to stimulus intensities that wouldnormally be considered subthreshold to the neuron in the absence ofnoise. Both electrical and mechanical modalities of bias signal, usedindividually or in combination, may be used to effect the lowering ofsensory neuron detection threshold.

SUMMARY OF THE INVENTION

[0016] In a preferred embodiment, provided is a method of enhancingsensorimotor performance in a subject comprising inputting at least onebias signal to at least one sensory cell area of a subject while thesubject is performing a pre-defined physical activity which utilizessensory cells within the sensory cell area and which are involved in thesensorimotor performance to be enhanced. By inputting the bias signal inaccordance with this method the function of the sensory cells isimproved. In combination with physical activity, enhancements tosensorimotor performance result. Enhancements effectuated using themethod of the present invention include, for example: improved jointstability, improved gait, improved balance, improved motor learning, andimproved motor skill.

[0017] The bias signal applied to the subject may modulated in responseto a measured physical variable measured from at least one body segmentof the subject during the pre-defined physical activity. The physicalvariable is selected from force, pressure, position, angle, velocity,and acceleration. The bias signal may also be modulated in synchronywith the pre-defined activity. In a preferred embodiment, the biassignal is a mechanical or an electrical signal. The preferreddisplacement of mechanical signals is about 1 μm to about 10 mm. Thefrequency of the mechanical signals is preferably within the range ofabout 0 Hz to about 1000 Hz. The current density of electrical signalsis preferably in the range of about 1 μA/in2 to about 1000 μA/in². Thefrequency of the electrical signal is preferably within the range ofabout 0 Hz to about 10,000 Hz.

[0018] In yet another embodiment, provided is a system for enhancingsensorimotor performance in a subject. The system is preferablycomprised of a wearable device and a signal generator. At least onerepositionable input signal is secured to the wearable device. Thesignal generator is communicatively coupled to the signal input deviceand includes a power source, a signal processor, and a controller. Thesignal generator may be repositionable and removably attached to thewearable device. The signal processor may include a calibration modulefor adjusting the bias signal produced by the signal processor. Thewearable device preferably forcibly presses the signal input device tothe subject's skin surface. To this end, the wearable device ispreferably constructed from stretchable fabrics or materials.Furthermore, the signal input device is electrically connected to thesignal generator. The means by which the signal input device iselectrically connected is preferably housed within, and therebyprotected by, the structure of the wearable device.

[0019] In addition to improved sensorimotor performance, improvements inneuroplasticity and an increase in growth hormone production can beachieved using the method and apparatus of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020]FIG. 1 is a flow chart of a method for enhancing the function of asensory cell;

[0021]FIG. 2 is a flow chart of a method of locating an input area;

[0022]FIG. 3 is a flow chart of a method of generating a bias signal;

[0023]FIG. 4 is a schematic depiction of a system for enhancing thefunction of a sensory cell;

[0024] FIGS. 5A-5C illustrates an system for enhancing sensorimotorperformance;

[0025]FIG. 6 is illustrates a signal generator of the present invention;

[0026]FIG. 7 illustrates wearable device, as one embodiment of thepresent invention;

[0027]FIG. 8A-8B illustrate wearable device, as another embodiment ofthe present invention; and

[0028]FIG. 9 illustrates a signal input device of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] The preferred embodiments of the present invention provide amethod and system for improving sensorimotor performance of humans,non-human mammals, and non-mammalian animals, hereinafter termed“subjects.” Improvements in sensorimotor performance are meant toinclude immediate or acute effects, such as improved dynamic jointstability, and more durable effects as would result from neuroplasticchanges in the PNS or CNS. The method comprises inputting a bias signalto sensory cells of the subject, so as to improve the function of thosesensory cells by effectively lowering their threshold of firing, whilethe subject engages in pre-defined physical activity. Acting inconjunction with this preferred method is a preferred apparatus thatcomprises a wearable device and other electromechanical components thatprovide a convenient and secure means of delivering the bias signal tothe subject. As used herein, the term “bias signal” will be taken tomean a subthreshold form of stimulation to a sensory neuron, whetherelectrical or mechanical in nature, whose waveform may be periodic,aperiodic, deterministic, or non-deterministic and may contain one ormany frequencies.

[0030] The method and system according to the preferred embodiments ofthe present invention are useful, for example, to enhance sensorimotorfunction in healthy individuals as well as in individuals withdisorders, diseases and/or injuries. For example, the method and systemcould be used by healthy individuals striving to learn a new motorskill, such as might be required for athletic activity. In anotherexample, the method and system could be applied to individuals withelevated sensory thresholds or other neurological dysfunction, such asmight arise from aging, peripheral neuropathies, or strokes.

[0031]FIG. 1 is a flow chart of a method for enhancing the function of asensory neuron according to one embodiment of the present invention. Instep 102, an area associated with the sensory cell whose function is tobe enhanced and to which a bias signal is to be input is located. Thelocated area is hereinafter referred to as the input area. Once theinput area has been located, the bias signal is generated in step 104.Then in step 106, the bias signal is input to the input area so as toeffectively lower the threshold of sensory cells with which the inputarea is associated.

[0032]FIG. 2 is a flow chart showing one embodiment of locating an inputarea according to step 102. Locating the input area depends, inter alia,on the sensory system whose function is to be improved and the method bywhich a bias signal may be input to sensory cells associated with thesensory system. Step 202 is a preliminary step in which anidentification scheme is undertaken to identify a particular sensorysystem whose function is to be enhanced. The identification scheme, tosome extent, depends on the cooperation of the individual. That is, thisstep is similar to a diagnosis, however, the individual need not besuffering from any disease or disorder to be subject to the enhancementprocess contemplated herein. In one embodiment, the sensory system whosefunction is to be enhanced is one whose function has been degraded bydisease.

[0033] In an alternative embodiment, the sensory system to be enhancedis one that functions normally. In step 204, the most appropriate way ofinputting a bias signal to the target sensory system is determined. Themost appropriate input means depends on a number of factors including,the target sensory system, the nature of the transduction system for thetarget sensory system, the present state of the target sensory system(i.e., whether it is impaired or in any way dysfunctional), and thenature of the signal which is to be determined (e.g., the amplitude andfrequency content of the signal). Input means that are appropriate incertain circumstances include, but are by no means limited to, nervecuffs, implanted electrodes, surface electrodes, muscle stimulators,tendon stimulators and magnetic field stimulators.

[0034] Once the most appropriate input means is determined in step 204,the input area is determined in step 206. The location of an input areadepends on the same factors as the determination of the most appropriateinput means. The location of the input area, however, varies for aparticular input means depending on, among other factors, whether thetarget sensory system is in any way dysfunctional, the cause andlocation of any such dysfunctionality, and the nature of the stimulatorto be used. More specifically, if a dysfunctionality caused by somephysical damage to sensory cells is present in the sensory system, itmay be necessary to locate the input area such that the bias signal willbypass the physical damage causing the dysfunctionality. Further, thefact that some stimulators, e.g. implanted electrodes, may requireinvasive procedures while others, e.g., surface electrodes, require onlynon-invasive procedures is also a factor to consider.

[0035] Once the input area is determined and the input means installed,the bias signal to be input is generated. FIG. 3 shows one embodiment ofa method of generating a bias signal. In an initial step 302, the biassignal is calibrated. That is, an optimal level for the bias signal isdetermined. Depending on the determinations of steps 204 and 206, thereexists a particular form of bias signal for which the signal detectionability of a given neuron in the target sensory system is optimallyenhanced. For example, a bias signal having parameters with certainpredetermined values will give rise to optimal enhancement. Calibrationhelps to ensure that certain parameters of the bias signals generatedwill be adjusted to achieve optimal enhancement. Examples of signalparameters of the bias signal that may be calibrated are amplitude,frequency, offset (D.C. bias), intensity, variance, frequency bandwidthand spectral characteristics in general. Calibration is typicallyaccomplished prior to installation of the enhancement system and may beaccomplished intermittently while the enhancement system is installed.If calibration is to take place while the enhancement system isinstalled, then it is desirable to install the enhancement system so itis accessible from the outside of the body so that calibration may beaccomplished non-invasively.

[0036] In one embodiment, the calibration is accomplished by inputtingan input signal of interest to a sensory cell coupled with a bias signalproduced by the enhancement system. The response of the sensory cell tothe combined input is recorded as a function of a parameter of interestin the bias signal. That is, the response of the sensory cell isrecorded as a parameter of interest in the bias signal is modulated.Using the recorded results, the coherence between the combined input andthe response of the sensory cell is then characterized by computing somemeasure such as the cross-correlation coefficient described below. Theresponse of the sensory cell is maximally enhanced when the coherencemeasure is maximized. This maximally enhanced response corresponds tosome value or range of values of the bias signal parameter of interestthat can be determined by, for example, examining a record of the biassignal. Thus, an optimal value or range of values for the parameter ofinterest of the bias signal is determined. The process can be repeatedusing other input signals and parameters of interest thereby determininga bias signal with optimal parameters for input signals with varyingparameters.

[0037] According to one embodiment of the present invention, the biassignal is optimized by examining the cross-correlation coefficient, C₁:$\begin{matrix}{C_{1} = \frac{C_{0}}{\sqrt{\overset{\_}{S^{2}(t)}}\sqrt{\overset{\_}{\left( {{R(t)} - \overset{\_}{R(t)}} \right)^{2}}}}} \\{where} \\{C_{0} = \overset{\_}{{S(t)}{R(t)}}}\end{matrix}$

[0038] where S(t) is the input signal, R(t) is the output of the sensoryneuron or sensory system (e.g., the neural mean firing rate signal orthe neural spike train), and the overbar denotes an average over time.S(t) and R(t) can be measured with any appropriate transducers, forexample, a needle electrode may be used to measure the output of aneuron. Maximizing C₁ corresponds to maximizing the coherence betweenthe input signal S(t) and the neuron's output R(t). The value of C₁ fora given input signal will depend upon the parameter of interest of thebias signal. Thus, a bias signal having parameters which will producethe desired output R(t) may be determined.

[0039] The results of the calibration process may be utilized, forexample, by modulating the bias signal in response to an input signal orby determining a set of parameter values which, on average, will achieveoptimal enhancement for any input signal. In the first instance,parameter values for the bias signal are, for example, tabulated againstparameters of the input signal. Upon occurrence of an input signal,certain parameters of the input signal are measured, and a bias signalhaving corresponding parameter values is generated by, for example,referencing the tabulated results. In this way, the bias signal ismodulated or optimized for each particular input signal. In the secondinstance, a single set of parameter values which will achieve optimalenhancement for most signals is calculated and used to generate a biassignal which is for use in response to every input.

[0040] After the input device has been calibrated and installed, in oneembodiment, an input signal to the neuron is detected. As will beexplained in conjunction with FIG. 4, one embodiment of a system forenhancing the function of a sensory neuron includes signal detectioncapabilities, for example, a transducer and signal processor. Thus, instep 304, input signals to the neuron are detected using the signaldetection capabilities.

[0041] Once an input signal is detected in step 304, a bias signal isgenerated in step 306. As explained above with respect to thecalibration process, the bias signal has either parameters which aremodulated depending on certain parameters of each input signal or aconstant, non-modulated, set of parameters which are designed tooptimally enhance the function of a sensory cell in response to mostinput signals. If a bias signal having a non-modulated set of parametersis used, then a somewhat simpler input system is used. In general, thenature of the bias signal to be used, that is, modulated ornon-modulated, depends on the nature of the sensory system to beenhanced. Once the bias signal is generated, it is input to the neuronin step 106.

[0042] In the embodiments described above, a bias signal is producedonly in response to the detection of an input signal to the neuron. Inan alternative embodiment, after the input device has been calibratedand installed, a bias signal is continuously generated and input to theneuron. That is, an input signal does not need to be detected. In amethod according to this embodiment, the bias signal is either modulatedor non-modulated. If the bias signal is modulated, then the continuouslygenerated bias signal is modulated as described above, when an inputsignal is detected. If a non-modulated bias signal is used in thisembodiment, then a simplified input system may be used. As discussedabove, whether a modulated or non-modulated bias signal is used dependsupon, inter alia, the nature of the system to be enhanced.

[0043] In another embodiment, a distributed enhancement process is used.In this embodiment, the enhancement process described above is modifiedsuch that a bias signal is generated and input to neurons at a pluralityof locations to stimulate an array of sensory cells and thereby providea distributed enhancement effect. In this distributed enhancementsystem, as above, either a continuous or non-continuous, and modulatedor non-modulated bias signals may be used. As one example, if thesensory function of the urinary tract is to be enhanced, a bias signalmay be input to a number of distributed points around the bladder sothat improved fullness sensation is obtained.

[0044] One embodiment of an enhancement system 400 for implementing themethod for enhancing the function of a sensory neuron is shown in FIG.4. Enhancement system 400 comprises a transducer 402, a signal processor404, an input device 408 and a controller 410. Enhancement system 400operates on electrical signals. An input signal to a sensory cell istypically initiated by contact with the outside world which contact isgenerally not in the form of an electrical signal. An input signal mightbe initiated by, for example, a touch, a movement of a body segment, asound wave or light. One function of transducer 402 is to detect inputsignal initiating contacts and convey the contact to enhancement system400 generally and signal processor 404 specifically. Another function oftransducer 402 is to convert an input signal initiating contact into asignal in a form that is usable by enhancement system 400. The mechanismused for transducer 402 depends on the sensory system targeted. As anexample, if the auditory system is being targeted for enhancement,transducer 402 may take the form of a stimulating electrode or an arrayof stimulating electrodes arranged in the vicinity of the ear. Asanother example, if the proprioceptive system is being targeted forenhancement, transducer 402 is a tendon stimulator, implemented by wayof a piezoelectric transducer, installed or attached via elastic strapsto a tendon or parent muscle associated with the sensory cells whosefunction is to be enhanced. As still another example, if the vibrationor touch-pressure sensation system is being targeted for enhancement,transducer 402 is a surface electrode installed or applied over the skinof the area of the body containing the cells to be stimulated. Such anelectrode is attached using flexible electrode/skin interfaces.

[0045] Signal processor 404 produces a bias signal to be input to thesensory system targeted for enhancement through input device 408. Signalprocessor 404 is electrically connected to transducer 402, input device408 and controller 410. As discussed above, a bias signal may be eithercontinuous or non-continuous and modulated or non-modulated. The form ofsignal processor 404 depends upon the desired form of the bias signal tobe produced. In one embodiment, where a non-continuous, modulated biassignal is desired, signal processor 404 preferably includes both signaldetection capabilities and look-up table capabilities to store parametervalues for the bias signal. In another embodiment, where a constant,non-modulated bias signal is desired, signal processor 404 does notnecessarily require signal detection capabilities and look-up tablecapabilities. In one embodiment, signal processor 404 is either aspecial function IC or a general micro-processor and is preferablysmall, lightweight and portable. Further, signal processor 404preferably includes signal conditioning and data acquisition abilities.In one embodiment, a PCMCIA chip or card is used as signal processor404.

[0046] Signal processor 404 also includes calibration module 406.Calibration module 406 enables adjustment of the bias signal produced bysignal processor 404. For example, for optimal enhancement, signalprocessor 404 produces a bias signal having predetermined parameters(for example, a predetermined amplitude and frequency) in response to aparticular signal received from transducer 402. If these predeterminedparameters of bias signal are not properly adjusted, the bias signalwill not optimally enhance the function of the targeted sensory system.Calibration module 406 enables these predetermined parameters to beadjusted so that an optimal bias signal is produced. Calibration istypically accomplished prior to installation of enhancement system 400and may be accomplished intermittently while enhancement system 400 isinstalled. If calibration is to take place while enhancement system 400is installed, then it is desirable to install signal processor 404 so itis accessible from the outside of the body so that calibration may beaccomplished non-invasively. In an alternative embodiment, signalprocessor 404 is provided with remote access capability enablingcalibration to take place non-invasively whether or not signal processoris accessible from outside of the body.

[0047] Input device 408 conveys the bias signal produced by signalprocessor 404 to the targeted sensory system. Depending on what thetargeted sensory system is, input device 408 might take a number ofdifferent forms as discussed above. Input devices that are appropriatein certain circumstances include, nerve cuffs, implanted electrodes,surface electrodes, muscle stimulators, tendon stimulators, and magneticfield stimulators. The manner in which input device 408 conveys the biassignal to the targeted sensory system depends on the form of inputdevice 408 and the targeted sensory system. For example, a nerve cuff orimplanted electrode is suitable for use when the urinary tract is thetargeted sensory system and is typically implanted surgically andconveys the bias signal to the sensory components of the system. Amuscle or tendon stimulator, on the other hand, is more suited tomechanically stimulate the proprioceptive system. Such a stimulatormechanically stimulates the proprioceptive system by vibrating a muscleor tendon associated with that system, for example a muscle in thevicinity of a joint. Muscle or tendon stimulators can be appliednon-invasively using, for example, an elastic band. In one embodiment,where the targeted sensory system is the vibration or touch-pressuresensation system, a surface electrode-based system is used as inputdevice 408. Specifically, the glove electrode, the sock electrode, andthe sleeve electrode, sold under the name ELECTRO-MESH[TM] may be usedas input device 408. The surface electrode system is placed over thebody part of interest, e.g., the hand or foot. Still further, inputdevice 408 may be a magnetic field stimulator used either non-invasivelyor invasively. For example, a magnetic field stimulator may be used tostimulate cutaneous sensory neurons by positioning the stimulator on theexterior of the body in the vicinity of the sensory cells to bestimulated using elastic bands. A magnetic field stimulator may be usedinvasively, for example, by surgically implanting the stimulator tostimulate sensory neurons in the area of the bladder.

[0048] Controller 410 controls interaction between transducer 402,signal processor 404 and input device 408. The implementation forcontroller 410 depends upon, among other things, the form of bias signaldesired. That is, where a non-continuous, modulated bias signal isdesired, controller 410 may be implemented using a microprocessor. In asimpler embodiment, where a continuous, non-modulated bias signal isdesired, controller 410 may be implemented using a switch that simplyactivates the enhancement signal. Alternatively, signal processor 404may be adequate, so that controller 410 is unnecessary for such anembodiment. By way of example only, controller 410 comprises amicroprocessor with suitable programming, or any digital controller. Inone embodiment, controller 410 is implemented with the aforementionedPCMCIA chip or card.

[0049] The nature and amplitude of the bias signal is controlled inaccordance with the type of sensory cell to which the bias signals areapplied. Repetitive waveform, pulse or DC signals of the type typicallyused for other types of injury treatment (e.g. pain suppression, bonehealing) are often be avoided in the practice of the present invention,as sensory cells can adapt to simple deterministic signals therebyreducing or eliminating over time the effect of such signals on thesensory cells. Instead, in accordance with the invention,non-deterministic noise signals, such as random, aperiodic noisesignals, or recorded repetitions of noise signals are preferably used,so that the sensory cells do not adapt to the noise signals over theextended period of noise signal application that occurs during aphysical training regimen. These signals can be continuously generatedsignals such as those created by known instruments, including a computerrandom number generator, a noise diode, or thermal noise from a resistoror other electrical component. Sampled signals, such as signals storedin a storage device (RAM, ROM, etc.), or periodically recorded noisysignals, may also be employed.

[0050] The sensory cell areas containing neurons to be affected by biassignals may be found at different depths in the human body, causingdifferent signal transmission filtering characteristics to exist betweencertain of the sensory cells and the signal input device. In a preferredembodiment, the bias signal can be combined with other signal types toovercome this problem. For example, a chirped signal can be formed byoverlaying a noise signal with a swept frequency signal that regularlysweeps through a signal frequency range. This combined signal may betailored to permit the amplification of frequency ranges that arenormally attenuated by transmission in the body. Thus, the signal iscompensated at the skin-surface level for expected attenuations thatwould occur prior to it reaching the target sensory cell. This techniquemight also be used to reduce the effort required to determine anefficacious signal since it might contain all desired frequency ranges.

[0051] Another method of the present invention involves enhancingvarious neurophysiologic functions by applying an externally producedbias signal to a sensory cell area, as described above, while thesubject is performing a pre-defined physical activity. Neurophysiologicfunctions enhanced by this method of the present invention include, forexample, limb position sense enhancement, increase release of growthhormones, enhanced peripheral neuroplastic changes, and enhancedcentral, including cortical, neuroplastic changes.

[0052] Most physical training regimens are undertaken to induce, amongother things, motor learning, i.e. the acquisition of new motor skillsor the regaining of motor skills that have been lost due to injury ordisease. To achieve the aforementioned sensorimotor performanceenhancements, while a subject performs a specified physical activitybias signals are applied to sensory cells involved in the specificphysical activity to lower the threshold at which such cells aretriggered by the external stimuli resulting from the activity. By makingthe sensory cells more responsive, the number of action potentialsproduced for any given amount of external stimuli is increased, therebyimproving the rate and/or quality of motor learning resulting from theactivity.

[0053] Coordinated motion of the extremities, for example, requiresprecise interplay between descending volitional signals from the brain,muscle contraction, limb movement, and interaction with the environment.This tight control is reliant, in part, on sensory feedback of amechanical nature from the extremities involved in the motion.Somatosensory information, e.g. tactile information from foot sole andproprioceptive information from knee joint, is clearly important both tonormal gait and to more vigorous activities such as jumping and landing.The method of the present invention is effective to boost coordinatedsensory information from the mechanoreceptors involved in limb positionsense during movement of the extremities. This added information contentduring movement provides a means for improved sensorimotor control. Suchimprovements result in enhanced balance, corrected gait patterns, andprevention of injuries by avoiding, for example, hyperextension ofjoints.

[0054] In one embodiment of the invention, a bias signal is providedduring a training regimen to a plurality of structures that participatein stability of a joint in a subject, to thereby promote joint sensationand feedback to enhance stability in the subject. For example, at leastone input device, e.g. an electrode, can be placed at or near thearticular space such that sensory cells in or adjacent to the ligaments,the joint capsule and meniscus, are stimulated. The bias signal isprovided at a level below the perception threshold of the sensory cellsassociated with the structures as well as below the cutaneous painthreshold.

[0055] In another preferred embodiment, the bias signal can be providedto at least two structures that maintain joint stability and are onopposite sides of the joint such that the performance of the sensorycells contained in these structures are enhanced. Preferably, a biassignal is provided at or adjacent to the joint and at least twodifferent antagonist muscles on opposite sides of a joint where theaction of these muscles determines the relative flexion and extension ofthe joint.

[0056] The bias signal can be provided simultaneously to each of thestructures or it can occur sporadically at each of the structures.Preferably, the bias signal is repeatedly provided to each of thestructures, e.g., the bias signal is repeated such that the bias signalis simultaneously provided to each of the structures or the bias signalis repeated such that the bias signal is sporadically provided to eachof the structures a plurality of times.

[0057] Specific bias signal ranges are applicable to specific types ofbias signals used in accordance with this invention. For example,electrical signals are preferably applied within a current density rangeof about 1 μA/in² to about 1000 μA/in² and a frequency range of about 0Hz to about 10,000 Hz the skin surface of a recipient. Mechanicalsignals preferably have a displacement at the skin surface within therange of about 1 μm to about 10 mm and frequencies within the range ofabout 0 Hz to about 1000 Hz. Mechanical signals can be remotelycontrolled by providing mechanical actuators on the skin surface thatreceive remotely generated waveform signals from a remote transmitterand convert these signals to mechanical signals. In wireless systems,electrical signals can also be transmitted from a remote transmitter toelectrodes that apply electrical signals to a subject. All bias signalsare preferably designed to allow for complex constructive and/ordestructive patterns.

[0058] Naturally-occurring growth hormones, as another example, arereleased in humans by the pituitary gland. These hormones are part ofthe body's system of changing the architecture of muscle and bone inresponse to changes in activity. For example, increases in muscle bulkin response to exercise are partly caused by increased amounts ofcirculating growth hormone in the body. Recent research has establishedthat afferent signals from the periphery, specifically those arisingfrom muscle, spur release of specific types of growth hormone from thepituitary (McCall, et al., 2000). In accordance with the presentinvention, sensory feedback neurons are made more active by applyingbias signals to lower the sensory cell threshold during a physicaltraining regimen. As a result, afferent traffic from the periphery isincreased, which causes neuroplastic changes in the brain. For example,sensory information from muscle spindles that boost release of growthhormone in response to activity is increased. This is especiallybeneficial to individuals, e.g. strength trainers, working to regainmuscle bulk and bone integrity following trauma or prolonged periods ofinactivity. In some cases, the increase in growth hormone release may besufficient to eliminate the need for growth hormone replacementtherapies and the need for growth hormone supplements.

[0059] Interconnections and efficiency of sensorimotor pathways in theperiphery are a manifestation of the acquisition of new motor skills.That is, a key result of training and practice is the creation of thesenew pathways. Indeed, even increases in strength are due as much toneurologic changes as to increases in muscle mass, especially early instrength building regimens. Recent research has shown that afferentactivity spurs the creation of new synapses (“synaptogenesis”), one ofthe underlying neurophysiologic processes of peripheral neuroplasticity(Wong, et al., 2000). Applying bias signals to an input area inaccordance with the method of the present invention increasesinformation-rich sensory traffic from the periphery drives neuroplasticchanges in the periphery. A common perception of strength training isthat it involves only muscularity, and that neurology is not aconsideration. In actuality, neurological factors are central to thedevelopment and maintenance of muscular strength. In the initial stagesof a strength training regimen, muscle mass does not increasesignificantly but strength does as a result of the neuromuscularlearning process. By applying bias signals to an input area inaccordance with the method of the present invention, the time forcompleting this process is significantly reduced by lowering thethreshold for the sensory cells involved during this stage of thestrength training. As a result, information-rich traffic from theperiphery drives neuroplastic changes in the periphery that, among otherthings, increases the rate by which muscle mass formed.

[0060] Strength training performed in accordance with the presentinvention is also effective in enhancing crossover strength changes inhuman appendages such as the arms or the legs. Strength trainingresearch has shown that when only one appendage is subjected to astrength training regimen, the strength of the untrained appendageincreases to some degree. Thus, if one appendage is immobilized by acast or brace, the strength of the immobilized appendage can be enhancedby using the method of the present invention to lower the sensory cellthresholds in the opposite appendage during a strength training regimenfor the opposite appendage.

[0061] Many athletic training programs are directed to the improvementof balance that is required when weight is rapidly transferred from sideto side. Balance enhancement training regimens have included prolongedrepetitive side-to-side motion to promote motor learning that results inenhanced balance. Again, in combination with this side-to-side trainingregimen, the present invention involves lowering affected sensory cellthresholds during the training to achieve with greater rapidity enhancedbalance.

[0062] Moreover, both normal acquisition of new motor skills, and theprocess of regaining motor skills following injuries such as stroke,rely on the elimination and creation of new connections throughout thesensory and motor cortices. Recent research has established that sensoryactivity from the periphery is one of the underlying drivers of thesebeneficial neuroplastic changes in the brain (McKay, et al., 2002).Applying a bias signal to an input area in accordance with the method ofthe present invention also increases afferent traffic therebyaccelerating the improvement of motor skills.

[0063] FIGS. 5A-5C, illustrate one preferred system for applying inputsignals in accordance with the method of the present invention asapplied during a physical training regimen. The system comprises a lowerextremity garment 500 that extends from the waist of a user down bothlegs. A belt 502 secures the garment at the waist while foot straps 504which extend beneath the user's feet hold the garment snugly against thebody during lower body motion. Foot straps are preferably composed ofneoprene or other known elastic material. Garment 500 preferablyincludes a plurality of belt straps 506 positioned circumferentiallyaround the waist section of the garment 500. The loose ends of straps506 fold over belt 502 and attach to garment 500 via Velcro or otherknown fastening means to, in effect, form a belt-loop that securelyretains belt 502 at waist level.

[0064] Garment 500 is designed for the application of input signals atand below the knee. Consequently, the legs of the garment have closures508 that permit input device 510 to be positioned at selected positionsrelative to the knee, calf and/or lower leg muscles while also beingmaintained in place to garment 500. External caps 511 clip through thegarment and onto input device 510, so as to securely hold input device510 in place. Signal input devices 510, therefore, can be placed atvirtually any position on the garment as necessary for variousapplications and to accommodate the anatomy of the subject. To fitgarment 500 to a user, input devices 510 are first placed on the skin ofa user relative to specific muscles, joints, etc. Garment 500 is thencarefully donned over input devices 510 and external caps 511 areclipped through garment 500 to hold input devices 510 in place. Garment500 is preferably formed of neoprene or any known stretchable materialthat enables the garment to closely conform to the subject and securelyhold the input devices 510 securely against the subject's skin toprevent displacement of the input devices 510 during the prolongedmotion involved in an exercise regimen.

[0065] Cables 512 electrically connect the input devices 510 to a signalgenerator 514. Signal generator 514 provides power to input device 510on the inner surface of the garment so that changes in the position ofthe electrodes can be adjusted within the area of input devices 510.Cables 512 are preferably secured to garment 500 such that there are noloose cables to impede body movement. In a preferred embodiment, cables512 extending from signal generator 514 are secured within side pockets516 of garment 500. Cables 512 extend through pockets 516 into a conduit520 that extends downward along the leg portions of garment 500. Conduit520 branches into multiple conduits at knee level, so as to accommodateinput devices 510 positioned at various positions on and about the lowerleg. Input devices 510 can be attached at any position along the lengthof cables 512. A cable guide 522 made of plastic or similar materialsurround conduit 520 so as to maintain the opening of conduit 520 intopocket 516. The conduit opening maintained by cable guide 522 allowscable 512 to be fed into and out of the length of conduit 520 withconsiderable ease.

[0066] Cable 512 is preferably of sufficient length to permit controller514 to slide from the side of belt 502 to the back of the belt 502.Thus, signal generator 514 can be repositioned at various positionsalong belt 502, so as not to restrict movement required by specificexercises. Signal generator 514 can also be worn at other locations orhand held. Generally, the placement of signal generator 514 isdetermined based upon location of the joint to be stabilized, thecomfort of the subject and/or the ease of motion by the subject. Toeliminate cables 512, signal generator 514 may include one or morewireless transmitters operative to transmit signals to signal generator514 and/or input devices 510.

[0067] Signal generator 514, as shown in FIG. 6, includes a signalprocessor 404, a controller 410, control dials 606, a display 608, atest button 610, and an infrared port 612. Display 608 shows graphicinformation that is of interest to the user or clinician such as currentstimulation program, remaining battery life, stimulation levels, activechannels, errors etc. Infrared port 612 (or wireless or cabled, etc.)provides a link to a computer station that permits the downloading ofcustom stimulation patterns and waveforms. Test button 610 permits theconfirmation of appropriate controller function. Controls dials 606 areoperative to vary the amplitude of the noise signals provided to thesignal input devices 510 so as to maintain the signals below thethreshold level of the sensory cells targeted, as well as below thesubcutaneous threshold level. The electrical current density at eachsignal input device 510 is determined by the current amplitude and thesize of the electrode. The current density must be maintained within anacceptable range. In the case of electrical stimulation, channels may beelectrically isolated from one another or may share a common ground.

[0068] Input devices 510 can apply, through the skin, input signals tothe structure associated with joint orientation. As earlier noted, theinput devices 510 in the garment can be surface electrodes, musclestimulators, tendon stimulators, and magnetic field stimulators,vibratory stimulators, e.g. small electromagnetic rotary motors or flatmotors (i.e. pancake motors), piezoelectric actuators, ferrofluidmagnetic actuators, or electrorheologic actuators, or other known signalinput device The signal input devices are appropriately sized andarranged to localize stimulation to a desired structure. For example,knee electrodes and actuators are sized as to not impede or restrictmotion and to limit (target) the stimulation to the sensory neurons ofinterest. Signal generator 514 can be programmed to vary the intensityand timing of the signals. For example, when more than one input device510 is used, the location and polarity of the signals can be varied.Similarly, the stimulation can simultaneously occur at each of inputdevices 510, or the stimulation can occur sporadically between each ofinput devices 510. The power and frequency of stimulation can also becontrolled. The signal is at a level below the perception threshold ofsensory cells associated with the various structures that play a role inthe joint's stability. Thus, the signal is at a level below thatrequired to trigger the sensory cells in those structures.

[0069] The level of the signal supplied by signal generator 514 may alsobe enough to stimulate other cells that are located in structures notdirectly involved in joint stability. For example, sensory cells withinthe skin may perceive a signal supplied through an input device 510placed upon the skin, but the level is still below the thresholdrequired to stimulate the sensory cells of the structure, e.g., such asthe hamstring below the skin, which is associated with the stability ofthe knee joint. Such low level signals are described in Collins et al.,U.S. Pat. No. 5,782,873.

[0070] In another preferred embodiment, provided is a structure 700 forplacing signal input devices 510 in contact with the subject's skin, asshown in FIG. 7. A plurality of arms 704 extend from central hubs 708which, when structure 700 is properly worn, are positioned on oppositesides of the joint of interest. The portion of arms 704 immediatelyadjacent to the central hubs 708 is composed of an expandable material,e.g. rubber. Arms 704 are preferably biased inwards inward to a degree,such as to securely engage the leg when structure 700 is positioned onthe extremity. Arms 704 also include a plurality of input devices 510positioned such that when structure 700 is properly positioned on theextremity, input devices 510 are positioned on those areas of the legwhere the bias signal is to be applied in accordance with the method ofthe present invention.

[0071] At least one of the arms 704 includes a cable outlet 706 that iselectrically wired to each of input devices 510. Outlet 706 accommodateselectrical connector 702 of cable 512 such that when the other end ofcable 512 is connected to signal generator 514, an electrical connectionis established between signal generator 514 and input devices 510. Cable512 is preferably composed of a stretchable and strain resistantmaterial to reduce the likelihood of cable 512 becoming detached fromoutlet 706 or signal generator 514 during use.

[0072] In another aspect of the invention, provided is a joint coveringstructure 800, as shown in FIGS. 8A-8B on a knee joint, having aplurality of input devices 510, and preferably a signal generator 514,incorporated into or positioned thereon. Input devices 510 arepositioned so as to engage the appropriate combination of muscles andjoints to which the bias signal is to be applied in accordance with themethod of the present invention. Joint structure 800 is preferablydesigned to wrap around the joint and fasten upon itself by Velcro orother known fastening means. Alternatively, joint structure 800 can beconfigured to slide onto and off of the joint. Joint structure 800 ispreferably made of fabric, but can also be made of plastic, rubber, orother material, as long as at least a portion of the structure is madeof a flexible material which allows the input devices 510 to remain inplace during the flexing and extending of the joint. As illustrated, theridged portion 802 of structure 800 is comprised of thicker materialcapable of assistively bracing the joint. A thinner portion 804 ofstructure 800 is positioned over the joint so as to allow bending of thejoint without displacing the input devices 510.

[0073] In another aspect of the invention, provided is an electrodeapplicator 900, as shown in FIG. 9, which provides a means to customizethe position of, or distance between, signal input devices 510 (e.g.skin surface electrodes) for a subject receiving treatment in accordancewith the method of present invention. Areas of flexible, electricallyconductive layer 902, such as conductive rubber, provide an electricallyconductive means between wires 908 and signal input devices 510.Covering and surrounding the conductive layer 902 on the outer surfaceof the structure is a nonconductive material 904. These two layers ofconductive 902 and non-conductive materials 904 are permanently affixedto one another. Also covering conductive layer 902 on its inner, or skinsurface, side is a non-conductive film 906 which is removably affixed tothe conductive layer 902. By removing non-conductive film 906, the innersurface of conductive layer 902 is exposed, allowing a signal inputdevice 510 to be affixed to the conductive layer 902. Non-conductivefilm 906 is scored or otherwise segmented in a pattern which allows forportions of the non-conductive film 906, rather than the entire film, tobe removed. In this way, the majority of the conductive layer 902remains covered by the non-conductive film 906 during use. Signal inputdevices 510 are composed of a thin, electrically conductive material,such as hydrogel, that provides the electrical interface between theconductive layer 902 and the subject's skin.

[0074] The apparatus used for performing the method of the presentinvention is unique relative to known units used for improvingsensorimotor performance (e.g. motor learning) or the treatment ofinjuries and rehabilitation from the effect of an injury. In such knownunits, electrodes are mounted on braces or wraps and include free,untethered electrical conductors, all of which will inhibit the motionrequired for the performance of an effective physical training regimen.

[0075] While the above illustrated embodiments are directed to pants, ajoint stabilizer, and a brace, the term wearable device as used herein,refers to any structure capable of holding input devices 510 in place ata desired location.

[0076] The embodiments described herein have been shown as a lower bodywearable device for illustrative purposes only. Similar embodimentscapable of holding signal input devices in place that are designed tothe upper body including the arms and torso of an individual, are withinthe spirit and scope of present invention. The upper body wearabledevice may be combined with the lower body wearable device to permitinput devices to be positioned and operated simultaneously along boththe upper and lower body in accordance with the method of the invention.

[0077] Although the present invention has been described in detail, itshould be understood that various changes, substitutions, andalterations can be made without departing from the intended scope asdefined by the appended claims.

What is claimed is:
 1. A method of enhancing sensorimotor performance ina subject comprising the step of: inputting at least one bias signal toat least one sensory cell area of a subject while said subject isperforming a pre-defined physical activity which utilizes sensory cellswithin said sensory cell area and which are involved in the sensorimotorperformance to be enhanced, wherein inputting said at least one biassignal improves the function of said sensory cells.
 2. The method ofclaim 1, wherein said sensorimotor performance is improved jointstability.
 3. The method of claim 1, wherein the sensorimotorperformance is improved gait.
 4. The method of claim 1, wherein thesensorimotor performance is improved balance.
 5. The method of claim 1,wherein said sensorimotor performance is improved motor learning.
 6. Themethod of claim 1, wherein said sensorimotor performance is improvedmotor skill.
 7. The method of any of claims 2-6, wherein thesensorimotor performance is enhanced through improved neuroplasticity.8. The method of claim 7, wherein said neuroplasticity is centralneuroplasticity.
 9. The method of claim 7, wherein said neuroplasticityis peripheral neuroplasticity.
 10. The method of any one of claims 2-6,wherein said sensorimotor performance is enhanced through increasedgrowth hormone release.
 11. The method of claim 1, wherein said biassignal is modulated in synchrony with said pre-defined physicalactivity.
 12. The method of claim 1, wherein said bias signal ismodulated in response to a measured physical variable measured from atleast one body segment of said subject during said pre-defined physicalactivity, wherein is said physical variable is selected from the groupconsisting of: force, pressure, position, angle, velocity, andacceleration.
 13. The method of claim 1, wherein said bias signal is amechanical signal having a displacement of about 1 μm to about 10 mm.14. The method of claim 1, wherein said bias signal is a mechanicalsignal composed of one or more frequencies within the range of about 0Hz to about 1000 Hz.
 15. The method of claim 1, wherein said bias signalis an electrical signal having a current density in the range of about 1μA/in² to about 1000 μA/in².
 16. The method of claim 1, wherein saidbias signal is an electrical signal composed of one or more frequencieswithin the range of about 0 Hz to about 10,000 Hz.
 17. A method ofenhancing sensorimotor performance in a subject comprising the step of:inputting at least one bias signal to at least one sensory cell area ofa subject while said subject is performing a pre-defined physicalactivity which utilizes sensory cells within said sensory cell area andwhich are involved in the sensorimotor performance to be enhanced,wherein inputting said at least one bias signal improves the function ofsaid sensory cells, and wherein said at least one bias signal isgenerated and inputted by a system for enhancing sensorimotorperformance, said system comprising a wearable device to which at leastone signal input device is repositionably secured, and a signalgenerator communicatively coupled to said at least one signal inputdevice for generating said bias signal..
 18. The method of claim 17,wherein said sensorimotor performance is improved joint stability. 19.The method of claim 17, wherein the sensorimotor performance is improvedgait.
 20. The method of claim 17, wherein the sensorimotor performanceis improved balance.
 21. The method of claim 17, wherein saidsensorimotor performance is improved motor learning.
 22. The method ofclaim 17, wherein said sensorimotor performance is improved motor skill.23. The method of any of claims 18-22, wherein the sensorimotorperformance is enhanced through improved neuroplasticity.
 24. The methodof claim 23, wherein said neuroplasticity is central neuroplasticity.25. The method of claim 23, wherein said neuroplasticity is peripheralneuroplasticity.
 26. The method of any one of claims 18-22, wherein saidsensorimotor performance is enhanced through increased growth hormonerelease.
 27. The method of claim 17, wherein said bias signal ismodulated in synchrony with said pre-defined physical activity.
 28. Themethod of claim 17, wherein said bias signal is modulated in response toa measured physical variable measured from at least one body segment ofsaid subject during said pre-defined physical activity, wherein saidphysical variable is selected from the group consisting of: force,pressure, position, angle, velocity, and acceleration.
 29. The method ofclaim 17, wherein said bias signal is a mechanical signal having adisplacement of about 1 μm to about 10 mm.
 30. The method of claim 17,wherein said bias signal is a mechanical signal composed of one or morefrequencies within the range of about 0 Hz to about 1000 Hz.
 31. Themethod of claim 17, wherein said bias signal is an electrical signalhaving a current density in the range of about 1 μA/in² to about 1000μA/in².
 32. The method of claim 17, wherein said bias signal is anelectrical signal composed of one or more frequencies within the rangeof about 0 Hz to about 10,000 Hz.
 33. A system for enhancingsensorimotor performance in a subject comprising: a wearable device towhich is secured at least one signal input device, wherein said at leastone signal input device is repositionable on said wearable device; and asignal generator for generating a bias signal, wherein said signalgenerator is communicatively coupled to said signal input devices. 34.The system of claim 33, wherein said signal generator includes a powersource, a signal processor and a controller.
 35. The system of claim 34,wherein said signal processor includes a calibration module foradjusting the bias signal produced by said signal processor.
 36. Thesystem of claim 33, wherein said wearable device forcibly presses saidsignal input device to the subject's skin surface.
 37. The system ofclaim 33, wherein said wearable device is composed of stretchablefabric.
 38. The system of claim 33, wherein said signal generator isrepositionable and removably attached to said wearable device.
 39. Thesystem of claim 33, wherein said signal input device is electricallyconnected to said signal generator.
 40. The system of claim 33, whereinsaid signal generator is communicatively coupled to said signal inputdevice by an electrical conductor, at least a portion of said electricalconductor being secured within said wearable device and protected bysaid wearable device.
 41. A method of improving neuroplasticity in asubject comprising the step of: inputting at least one bias signal to atleast one sensory cell area of a subject while said □ subject isperforming a pre-defined physical activity which utilizes sensory cellswithin said sensory cell area and which are involved in the sensorimotorperformance to be enhanced, wherein inputting said at least one biassignal improves the function of said sensory cells.
 42. The method ofclaim 41, wherein said neuroplasticity is central neuroplasticity. 43.The method of claim 41, wherein said neuroplasticity is peripheralneuroplasticity.
 44. A method of improving neuroplasticity in a subjectcomprising the step of: inputting at least one bias signal to at leastone sensory cell area of a subject while said subject is performing apre-defined physical activity which utilizes sensory cells within saidsensory cell area and which are involved in the sensorimotor performanceto be enhanced, wherein inputting said at least one bias signal improvesthe function of said sensory cells, and wherein said at least one biassignal is generated and inputted by a system for enhancing sensorimotorperformance, said system comprising a wearable device to which at leastone respositionable signal input device is secured, and a signalgenerator communicatively coupled to said at least one signal inputdevice.
 45. The method of claim 44, wherein said neuroplasticity iscentral neuroplasticity.
 46. The method of claim 44, wherein saidneuroplasticity is peripheral neuroplasticity.
 47. A method ofincreasing growth hormone release in a subject comprising the step of:inputting at least one bias signal to at least one sensory cell area ofa subject while said subject is performing a pre-defined physicalactivity which utilizes sensory cells within said sensory cell area andwhich are involved in the sensorimotor performance to be enhanced,wherein inputting said at least one bias signal improves the function ofsaid sensory cells.
 48. A method of increasing growth hormone release ina subject comprising the step of: inputting at least one bias signal toat least one sensory cell area of a subject while said subject isperforming a pre-defined physical activity which utilizes sensory cellswithin said sensory cell area and which are involved in the sensorimotorperformance to be enhanced, wherein inputting said at least one biassignal improves the function of said sensory cells, and wherein said atleast one bias signal is generated and inputted by a system forenhancing sensorimotor performance, said system comprising a wearabledevice to which at least one respositionable signal input device issecured, and a signal generator communicatively coupled to said at leastone signal input device.